Starting device for electric motors



Sept. 28, 1943. .J. L. FREEBERG STARTING DEVICE FOR ELECTRIC MOTORSFiled Jan. 15, 1941 mi im W W;

Patented Sept. 28, 1943 UNITED STATES PATENT OFFICE STARTING DEVICE FORELECTRIC MOTORS John L. Freiber Cincinnati, Ohio Application January 13,1941, Serial No. 374,223

8 Claims.

This invention relates to starting devices or starting rheostats forelectric motors.

Where motors are operated on circuits of constant potential, as isnearly always the case, by reason of the low armature resistance in allexcept very small motors, it is necessary to limit the flow of currentthrough the armature until the motor generates a sufficient counterE. M.F. to regulate the current automatically. This limitation of the currentduring starting is effected by rheostats which consist of resistancescapable of carrying the starting current for the limited period requiredby the motor to come up to speed. The resistance is arranged in steps sothat it can be cut out of the armature circuit step by step as thecounter E. M. F. increases with the speed.

The principal object of the present invention is to provide a new andimproved starting box or rheostat for the purpose mentioned, in whichsimplicity of construction, consistency of operation and economy inmanufacture as compared with starting boxes presently in use, areemphasized.

A further object of the invention is to provide a starting device of thecharacter mentioned, in which adjustments in order to obtain consistencyin operation, may, as compared with presently used boxes, be more easilyand simply made and maintained.

Another object of the invention is to provide a. starting box whichlends itself to compactness of construction, thus adapting it for useunder conditions where space is necessarily limited, as for instance insubmarine vessels.

With the foregoing and other objects in view, I

Figure 1 is a sectional view of a starting box constructed in accordancewith this invention, parts of the interior mechanism however being shownin elevation.

Figure 2 is a plan view of the series of contacts with portions of thecircuit completing mechanism.

Figure 3 is a section on line 33 of Figure 2.

Figure 4 is a. section on line 4-4 of Figure 1 on a reduced scale.

Figure 5 is a diagrammatic view of the electrical connections.

The numeral l indicates the casing of my new starting device,.saidcasing being provided with atop 2 having aflongitudinal slot 3 for thepurpose hereinafter mentioned. Mounted on brackets 4 and 5 in the asingl is an inclined bar 6 which is constructed of any. suitable rigidinsulating material. Mounted on the bar 6, and insue lated thereby fromeach other, is a series of con- !tact terminals 1 which are connected atsuitable intervals to the resistancefl by means of leads 8. One end ofthe resistance 8, that is the end con,- nected with the topmost contactI, is conne ted by means of a lead 1 ll with the armature of motor II.The coil (2 of arelease magnet I3 is in a shunt circuit with the lineand motor field in accordance with the, practicein various types ofstarting boxes presently in Mounted so as to extend through the slot 3of the top 2, is a hollow shaft or sleeve l4 which is adapted to slidein said slot, The shaft, 14 is provided with an operating handle l5 onits upper end, and rollers l6 and ll span the slot 3 and ride onrespectively the upper and lower surfaces of the top 2 so as to maintainthe shaft l4 in vertical relation above theseries of contacts I of thebar 6. Mounted in the lower end of the hollow shaft I4 is a hollowplunger l8, which telescopically slides freely in the bore of the shaft.A compression spring I9 is mounted in the shaft I4 and p n 8 so that heupp r e d 0i s id spring abuts the lower end of an adjusting screw 20 ine ope a n han le an h lo r nd a s h l r e d of lu ger. th s o eini t e tct m mber 2 ca ried by he o r .fsce o e pl n er i oc n act with h e s ane o t c 1-. The sp 9 s of s h nsile st n th ha it expansi e e i i nccorces el minal 2| positively in contact with either of the resistancebuttons 1, and this force is of course increased as the buttonssuccessively are placed at higher elevations, thus increasing the copression. The expansive energy of the spring is such, coupled with theinclination of the con-. tacts, as to move'the plunger downwardly alongthe contacts whenever the shaft I4 is relieved of a force, either manualormagnetic', tending to push or hold it at a point of elevation abovethe lowest or rest button 22 which is not in the circuit. The desiredtension is regulated initially and may from tune to time be read usteqby means or'tne adjustment screw 20. T e shaft l4 may be brought intothe 11118 circuit by means of a flexible lead 11 desired, however, Iprefer to use a bus bar 24 w th which the smart, I4 makes contact bymeans or a spring conductor 25,. An armature as is mounted on the shaftl4 in such position as to complete the magnetic ci cuit. of releasemagnet l3 when the shaft is in. its ex treme right position with thecontact 2i in circuit with the uppermost or full speed contact 7.

The operation of my new starting device will be apparent from theforegoing description to those skilled in the art to which the sameapperable the motor to attain speed in accordance with the usual custom.When the plunger and contact 2i reach the uppermost contact 7, all ofthe resistance is cut out and the motor is running" under the fullpotential. In this position the shaft 54 and with it, of course, theplunger and contact 2! are held by the contact of the armature 25 withthe release magnet it. When for any reason, as for instance the failureof the line current, the circuit through coil 32 is discontinued, themagnet l3 releases the armature 25, and the'compression of spring itcauses the plunger to be forced downwardly carrying the shaft withconnectedmechanism to the left end (as viewed in Figure l) of the slot 3where the contact 2! rests on the open circuit button 22.

From the foregoing descriptionit will be observed that the' operation ofmy new starting rheostat depends on but one possible variable, that isthe compression of spring E9. The angle of the bar 6 and its contacts Iand the compressive energy of the spring having been predetermined intheir interrelation, and such angle being at all times definitelymaintained by the mounting of said bar on rigid brackets 4 and 5 in thecasing, the compressiveenergy of spring l9 should for indefinite periodsrequire no alterzontal vertical direction and passing centrally throughsaid support and with the contacting surfaces of said terminals in aplane parallel with the support, a contact member, means for mountingsaid contact member for movement in a linear direction in one of saidhorizontal or vertical planes in the direction of ascent of said contactsupport over said contact members while making sliding contacttherewith, compressible means for yieldingly holding said contactmemberv against said contact terminals during the movement of thecontact member, said angle of inclination of contact terminals withrespect to the plane of movement of the contact plunger and the force ofthe spring means on the contact planebeing such as to cause the contactplunger to automatically descend to the lowermost conation. However, Iprefer to provide adjustability for such compressive energy by means ofthe adjusting screw 29, so that the device may be readily adapted toindividual or local conditions and variations easily compensated.

It will be further observed that the mounting of-the series ofresistance buttons in alignment upon an inclined non-conductive barfacilitates great compactness of over-allconstruction, as well aseconomy of dielectric material as compared with the-usual arcuate seriesof contacts arranged about the center of a rotating shaft. Thisconstruction further contributes toeconomy and durability andconsistency of operation in the use of a single spring as againstthe'two or more springs usually employed in starting boxes of currenttype. 7

While I have described a preferred. application of the principle of myinvention, I do not of course desire to be limited to the specificdetails shown and described but consider as of my inventio-n all suchequivalents and similar constructicns as come within the preview of theappended claims. It should also be understood that the present inventionis intended for other types of switches, as for instance in lightingswitches for theatres, etc. I v a Having thus fully described myinvention, what I claim as new and desire to secure by Letter'sPatent'i's't' liIn adevice' of the character specified, incombinationwith a resistance, a seriesof contact terminals electricallyconnected at intervais with said resistance, a'support for saidterminals arranged in an inclined position with respect planes at rightangles to one'another in an horitact terminal, and means for holding thecontact member in position for maintaining contact with the uppermostcontact terminal.

2. In a device ofthe character specified, in combination with aresistance, a series-ofcontact terminals electrically connected atintervals with said resistance, a support for said terminals arrangedinan inclined position with respect to planes at right angles to oneanother in an horizontal andvertical direction and passing centrallythrough said support, and with the contacting surfaces of saidterminalsin a plane parallel with the support, a contact member, meansfor mounting said contact member for movement in a lineardirection inone of said horizontal or vertical planes in the direction of ascent ofsaid contact support over said contact members while makingslidingcontact therewith, compressible means for yieldlngly holding saidcontact member against said contact terminals during the move ment ofthe contact member, said angle of inclination of contact terminals withrespect to the plane of movement of thecontact plunger and the force ofthe spring means on the contact plane being suchas to cause the contactplunger to automatically descend to the lowermost contact terminal meansfor adjusting the compression force of compressible means, and means forholding the contact member in position for maintaining contact with theuppermost contact terminal.

3. A starting device for electric motors comprising in combination acasing, a resistance, an insulating support within said casing andmounted at an angle of inclination to a horizontal plane through saidcasing, a series of contact terminals in alignment on said supportinsulated thereby from one another with their contact surfaces in aplane parallel with the support, a manually actuable contact plungermounted in said casing so as to move in the horizontal plane through thecasing over said terminals, spring means for yieldingly compressing saidcontact plunger against said Contact terminals'so as to make electricalcontact therebetweenduring the movement of said contact plunger, saidangle of inclination of the contact term nal with respect to the planeof movement of the contact plunger and the force bf the spring means onthe contact plunger being such as to cause the contact.

plunger'to automatically descend to the lowermost contact terminal, andmeans for holding the contact. plunger in position for making contactwith the uppermost contact'terminal.

4. A starting device for electric'hiotors comprising in combination acasing, a resistance, an insulating support within said casing andmounted at anangle of inclination to a horizon tal plane through saidcasing, a series of contact terminals in alignment on said supportinsulated thereby from one another with their contact surfaces in aplane parallel with the support, a manually actuable contact plungermounted in said casing so as to move in the horizontal plane through thecasing over said terminals, spring means for yieldingly compressing saidcontact plunger against said contact terminals so as to make electricalcontact therebetween during the movement of said contact plunger, meansfor adjusting the compression of said spring means, said angle ofinclination of the contact terminal with respect to the plane ofmovement of the contact plunger and the force of the spring means on thecontact plunger being such as to cause the contact plunger toautomatically descend to the lowermost contact terminal, and means forholding the contact plunger in position for making contact with theuppermost contact terminal.

5. A starting device for electric motors comprising in combination acasing, a resistance, an insulating support within said casing andmounted at an angle of inclination to a horizontal plane through saidcasing, a series of contact terminals in alignment on said supportinsulated thereby from one another with their contact surfaces in aplane parallel with the support, a manually actuable contact plungermounted in said casing so as to move in the horizontal plane through thecasing over said terminals, spring means for yieldingly compressing saidcontact plunger against said contact terminals so as to make electricalcontact therebetween during the movement of said contact plunger, saidangle of inclination of the contact terminals contacting surfaces withrespect to the plane of movement of the contact plunger and the force ofthe spring means on the contact plunger being such as to cause thecontact plunger to automatically de scend to the lowermost contactterminal, and an electro-magnet for holding said contact plunger inposition for making contact with the uppermost contact terminal.

6. A starting device for electric motors comprising in combination acasing, a resistance, an insulating support within said casing andmounted at an angle of inclination to a horizontal plane through saidcasing, a series of contact terminals in alignment on said supportinsulated thereby from one another with their contact surfaces in aplane parallel with the support, a manually actuable contact plungermounted in said casing so as to move in the horizontal plane through thecasing over said terminals, spring means for yieldingly compressing saidcontact plunger against said contact terminals so as to make electricalcontact therebetween during the movement of said contact plunger, saidangle of inclination of the contact terminal with respect to the planeof movement of the contact plunger and the force of the spring means onthe contact plunger being such as to cause the contact plunger toautomatically descend to the lowermost contact terminal, and means forholding the contact plunger in position for making contact with theuppermost contact terminal, a bu bar mounted in said casing, and acontact carried by the contact plunger to make slidable contact withsaid bus bar simultaneously with the contact of plunger with theterminal contacts.

7. A starting device for electric motors comprising in combination aresistance, a casing, a cover on said casing, said cover being providedwith an elongated aperture, an insulating support mounted in said casingat an angle of inclination in relation to the cover, a series of contactterminals mounted in alignment on said support insulated thereby fromone another with their contacting surfaces in a plane parallel with saidsupport and electrically connected at intervals with said resistance,said terminals being in alignment with and under said aperture, a hollowshaft extending through the cover aperture, means for mounting saidshaft in the aperture for movement in the direction of its major axis, acontact plunger telescopically within said shaft and having its lowerend arranged to make sliding engagement with said contact terminalscontacting surfaces, a compression spring in said hollow shaft adaptedto force the contact plunger against said contact terminals during themovement of the hollow shaft, said angle of inclination of the contactterminals contacting surfaces and the force of the compression spring onthe contact plunger being such as to cause the contact plunger toautomatically descend to the lowermost contact terminal and means forholding said plunger in position for making contact with the uppermostterminal contact.

8. A starting device for electric motors comprising in combination aresistance, a casing, a cover on said casing, said cover being providedwith an elongated aperture, an insulating support mounted in said casingat an angle of inclination in relation to the cover, a series of contactterminals mounted in alignment on said support insulated thereby fromone another with their contacting surfaces in a plane parallel with saidsupport and electrically connected at intervals with said resistance,said terminals being in alignment with and under said aperture, a hollowshaft extending through the cover aperture, means for mounting saidshaft in the aperture for movement in the direction of its major axis, acontact plunger telescopically within said shaft and having its lowerend arranged to make sliding engagement with said contact terminalscontacting surfaces, a compression spring in said hollow shaft adaptedto force the contact plunger against said contact terminals during themovement of the hollow shaft, said angle of inclination of the contactterminals contacting surfaces and the force of the compression spring onthe contact plunger being such as to cause the contact plunger toautomatically descend to the lowermost contact terminal, and anelectromagnet for holding said plunger in position for making contactwith the uppermost terminal contact.

JOHN L. FREIBERG.

